Radio terminal, base station, and method therefor

ABSTRACT

In one implementation, a NAS layer (202) of a radio terminal (1) obtains, from an AS layer (208) of the radio terminal (1), either or both of: information regarding one or more access barring categories (401) broadcasted by a serving network (2); and the number of the one or more access barring categories. If barring information corresponding to a first access barring category (404) to which an application that triggers a session establishment (403) belongs is not broadcasted by an eNB (2), the NAS layer (202) replaces the first access barring category (404) with a particular access barring category among the one or more access barring categories (401) broadcasted by the serving network (202).

TECHNICAL FIELD

The disclosure relates to a radio access network and, in particular, tobarring of an access from a radio terminal.

BACKGROUND ART

Non-Patent Literature 1 describes Application specific Congestioncontrol for Data Communication (ACDC). ACDC is an access controlmechanism for an operator to allow or prevent new access attempts fromparticular, operator-identified applications in a User Equipment (UE) inidle mode. Using ACDC, the operator can prevent or mitigate overload ofthe access network or the core network or both.

ACDC applies only to UEs in idle mode (e.g., RRC_IDLE) and does notapply to UEs in connected mode (e.g., RRC_CONNECTED). The home network(i.e., Home Public Land Mobile Network (HPLMN) or

Equivalent HPLMN) is able to configure a UE with at least four ACDCcategories. Each ACDC category is associated to particular,operator-identified applications, application group, or services.Provisioning of the ACDC categories in the UE is the responsibility ofthe home network, and the categorization is outside the scope of 3rdGeneration Partnership Project (3GPP). The operator of the home networkmay configure the ACDC categories, for example, in the UniversalSubscriber Identity Module (USIM). The operator of the home network mayconfigure the UE with the ACDC configuration using Open Mobile AllianceDevice Management (OMA-DM).

The serving network (i.e., HPLMN, Equivalent HPLMN, or Visited PLMN(VPLMN)) broadcasts control information which indicates barringinformation per ACDC category and also indicates whether a roaming UEshall be subject to ACDC control. The UE controls whether an accessattempt for a certain application is allowed or not, based on thebroadcasted barring information and the configuration of ACDC categories(i.e., mapping between the ACDC categories and the applications) in theUE.

When configuring the UE with the ACDC categories, the home networkproceeds as follows. Applications whose use is expected to be restrictedthe least shall be assigned the highest ACDC category. Applicationswhose use is expected to be restricted more than applications in thehighest category shall be assigned the second-to-highest ACDC category.Applications shall be assigned the third-to-highest ACDC category, andso on, in the same manner as the second-to-highest ACDC category.Applications whose use is expected to be restricted the most shalleither be assigned the lowest ACDC category, or not be categorized atall.

Applications on a UE that are not assigned to any ACDC category shall betreated by the UE as part of the lowest ACDC category configured in theUE. If the operator requires differentiation with respect to theseuncategorized applications, the operator should avoid assigningapplications to the lowest ACDC category. When applying ACDC, theserving network broadcasts barring information starting from the highestto the lowest ACDC category.

The home network and the serving network may use differentcategorization. Specifically, the number of ACDC categories in the UEmay not be the same as the number of ACDC categories broadcast by theserving network. This may happen, for example, when the UE is roamingand the number of categories broadcast by the serving network isdifferent from that of the home network. In this situation, the UEproceeds as follows.

If the serving network broadcasts more ACDC categories than the UE'sconfiguration, the UE shall use barring information for the matchingACDC categories, and shall bar uncategorized applications using thebarring information for the lowest category broadcast by the servingnetwork, and shall ignore barring information for unmatched categories.

If the serving network broadcasts barring information for fewer ACDCcategories than the UE's configuration, the UE shall use barringinformation for the matching ACDC categories and shall bar otherapplications (including applications belonging to unmatched ACDCcategories) using the barring information for the lowest categorybroadcast by the serving network,

A matching ACDC category is an ACDC category for which barringinformation is broadcast by the serving network and that has the samerank as the rank of a configured ACDC category in the UE. Meanwhile, anunmatched ACDC category is either an ACDC category for which barringinformation is broadcast by the serving network but with nocorresponding ACDC category configured in the UE, or an ACDC categoryconfigured in the UE but with no corresponding barring informationbroadcast by the serving network.

Non-Patent Literature 2 has suggested which layer (application layer,Non-Access Stratum (NAS) layer or Radio Resource Control (RRC) layer)should perform the UE's operation required for ACDC. Specifically,Non-Patent Literature 2 has introduced some options in which theapplication layer, the NAS layer, or the RRC layer performs ACDC check.The ACDC check is a determination of whether to allow an access attempttriggered by an application, based on the ACDC category to which theapplication belongs determined by the ACDC configuration in the UE andalso based on the barring information broadcasted by the servingnetwork.

For example in the option in which the NAS layer performs the ACDCcheck, upon receiving a session establishment request from upper layers,if the UE is in Evolved Packet System (EPS) connection management IDLE(ECM-IDLE) mode, the NAS layer operates to:

1. Determine the ID (OS App ID) of the application triggering therequest;2. Determine to which ACDC category this OS App ID belongs based on theinformation provisioned to the UE by the home network operator via OMADM or the USIM;3. Obtain the barring information for the given ACDC category from theRRC layer;4. Perform the ACDC check; and5. Proceed with the Service Request procedure if the ACDC check passes.

Non-Patent Literature 2 has suggested two options in which the RRC layerperforms the ACDC check. In one of the two options, upon receiving anaccess attempt request, if the UE is in RRC_IDLE state, the RRC layeroperates to:

1. Determine the ID (OS App ID) of the application triggering the accessattempt request;2. Determine to which ACDC category this OS App ID belongs based on theinformation provisioned to the UE by the home network operator via OMADM or the USIM;3. Perform the ACDC check based on the barring information for the givenACDC category obtained from System Information Block (SIB) information;and4. Proceed with the access attempt if the ACDC check passes.

Alternatively, in the other option in which the RRC layer performs theACDC check, upon receiving a session establishment request, if the UE isin EMM-IDLE mode, the NAS layer operates to:

1. Determine the ID (OS App ID) of the application triggering thesession establishment request;2. determine to which ACDC category this OS App Id belongs based on theinformation provisioned to the UE by the home operator via Open MobileAlliance Device Management (OMA-DM) or the USIM; and3. Pass the corresponding ACDC category along with the Service Requestand the call type to the RRC layer.

Next, upon receiving the Service Request with the call type and the ACDCcategory from the NAS layer, the RRC layer operates to:

1. Perform the ACDC check based on the barring information for thereceived ACDC category obtained from System Information Block (SIB)information; and2. Proceed with the access attempt if the ACDC check passes.

CITATION LIST Non Patent Literature

Non Patent Literature 1: 3GPP TS 22.011 V13.2.0 (2015-06), “3rdGeneration: Partnership Project; Technical Specification Group Servicesand System Aspects; Service accessibility (Release 13)”, June 2015

Non Patent Literature 2: 3GPP C1-150143, Qualcomm Incorporated,“Possible options for ACDC stage 3 specification”, February 2015

SUMMARY OF INVENTION Technical Problem

As described above, Non-Patent Literature 2 provides several options forinteractions among the application layer, the NAS layer, and the RRClayer when the UE performs ACDC. However, it is not clear how the UEoperates when the number of ACDC categories configured in the UE is notthe same as the number of ACDC categories broadcasted by the servingnetwork.

Specifically, as described above, Non-Patent Literature 1 describesthat, if the serving network broadcasts fewer ACDC categories than theUE's configuration, the UE uses the barring information for the matchingACDC categories and bars other applications using the barringinformation for the lowest (ACDC) category broadcasted by the servingnetwork. Therefore, when an application that triggers an access attemptbelongs to an “unmatched ACDC category,” the UE needs to regard theapplication as belonging to a particular ACDC category (e.g., the lowestACDC category) broadcasted by the serving network in order to performthe ACDC check on the application. However, the interaction among theapplication layer, the NAS layer, and the RRC layer for implementingthis operation by the UE is not clarified. Here, an “unmatched ACDCcategory” means an ACDC category configured in the UE but with nocorresponding barring information broadcasted by the serving network.

One of the objects to be attained by embodiments disclosed in thepresent specification is to provide an apparatus, a method, and aprogram that contribute to providing an operation within a radioterminal for handling a case in which a serving network does notbroadcast barring information corresponding to an access barringcategory (e.g., ACDC category) to which an application that triggers anaccess attempt belongs. It is to be noted that this object is merely oneof the objects to be attained by the embodiments disclosed herein. Otherobjects or problems and novel features will become apparent from thedescriptions in the present specification or from the appended drawings.

Solution to Problem

In a first aspect, a radio terminal includes at least one radiotransceiver and at least one processor. The at least one processor iscoupled to the radio transceiver and is configured to operate as anon-access stratum (NAS) layer providing mobility management and sessionmanagement and as an access stratum (AS) layer providing radio resourcecontrol. The NAS layer is adapted to obtain, from the AS layer, eitheror both of; information regarding one or more access barring categoriesbroadcasted by a serving network; and the number of the one or moreaccess barring categories. The NAS layer is further adapted to, ifbarring information corresponding to a first access barring category towhich an application that triggers a session establishment belongs isnot broadcasted by the serving network, replace the first access barringcategory with a particular access barring category among the one or moreaccess barring categories broadcasted by the serving network.Furthermore, the NAS layer is adapted to pass the particular accessbarring category along with a NAS message for the session establishmentto the AS layer. The AS layer is adapted to control whether to allow anaccess attempt triggered by the NAS layer based on barring informationbroadcasted by the serving network and corresponding to the particularaccess barring category.

In a second aspect, a method in a radio terminal includes:

(a) sending, from an access stratum (AS) layer to a non-access stratum(NAS) layer, either or both of: information regarding one or more accessbarring categories broadcasted by a serving network; and the number ofthe one or more access barring categories;(b) when barring information corresponding to a first access barringcategory to which an application that triggers a session establishmentbelongs is not broadcasted by the serving network, replacing, by the NASlayer, the first access barring category with a particular accessbarring category among the one or more access barring categoriesbroadcasted by the serving network;(c) passing, from the NAS layer to the AS layer, the particular accessbarring category along with a NAS message for the session establishment;and(d) controlling, by the AS layer, whether to allow an access attempttriggered by the NAS layer based on barring information broadcasted bythe serving network and corresponding to the particular access barringcategory.

In a third aspect, a radio terminal includes at least one radiotransceiver and at least one processor. The at least one processor iscoupled to the radio transceiver and is configured to operate as anon-access stratum (NAS) layer providing mobility management and sessionmanagement and as an access stratum (AS) layer providing radio resourcecontrol. The NAS layer is adapted to pass a first access barringcategory to which an application that triggers a session establishmentbelongs, along with a NAS message for the session establishment to theAS layer. The AS layer is adapted to, if barring informationcorresponding to the first access barring category received from the NASlayer is not broadcasted by a serving network, select, from one or moreaccess barring categories broadcasted by the serving network, aparticular access barring category instead of the first access barringcategory. The AS layer is further adapted to control whether to allow anaccess attempt triggered by the NAS layer based on barring informationbroadcasted by the serving network and corresponding to the particularaccess barring category.

In a fourth aspect, a method in a radio terminal includes:

(a) passing, from a non-access stratum (NAS) layer to an access stratum(AS) layer, a first access barring category to which an application thattriggers a session establishment belongs, along with a NAS message forthe session establishment;(b) if barring information corresponding to the first access barringcategory received from the NAS layer is not broadcasted by a servingnetwork, selecting by the AS layer, from one or more access barringcategories broadcasted by the serving network, a particular accessbarring category instead of the first access barring category; and(c) controlling, by the AS layer, whether to allow an access attempttriggered by the NAS layer based on barring information broadcasted bythe serving network and corresponding to the particular access barringcategory.

In a fifth aspect, a base station includes: a radio transceiverconfigured to communicate with a radio terminal located within a cell,and at least one processor coupled to the radio transceiver. The atleast one processor is configured to broadcast, in the cell, one or moreaccess barring categories, barring information for each of the one ormore access barring categories, and a mapping rule. The selectingincludes selecting, by the AS layer, the particular access barringcategory instead of the first access barring category, when barringinformation corresponding to the first access barring category specifiedby the call type is not broadcasted by the serving network, or when theAS layer cannot recognize the call type.

In a sixth aspect, a method in a base station includes broadcasting, ina cell, one or more access barring categories, barring information foreach of the one or more access barring categories, and a mapping rule.The mapping rule defines mapping between the one or more access barringcategories broadcasted by the base station and one or more accessbarring categories provisioned in a radio terminal.

In a seventh aspect, a program includes instructions (software codes)that, when loaded into a computer, causes the computer to perform themethod according to the above-described second, fourth, or sixth aspect

Advantageous Effects of invention

According to the above aspects, there can be provided an apparatus, amethod, and a program that contribute to providing an operation within aradio terminal for handling a case in which a serving network does notbroadcast barring information corresponding to an access barringcategory (e.g., ACDC category) to which an application that triggers anaccess attempt belongs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a configuration example of a radiocommunication network according to some embodiments;

FIG. 2 is a diagram illustrating an example of a protocol stack of acontrol plane of a radio terminal according to some embodiments;

FIG. 3 is a diagram illustrating a specific example of ACDC controlinformation;

FIG. 4 is a diagram for describing an ACDC operation performed by aradio terminal according to a first embodiment;

FIG. 5 is a flowchart showing an example of a NAS layer of the radioterminal according to the first embodiment;

FIG. 6 is a diagram for describing an ACDC operation performed by aradio terminal according to a second embodiment;

FIG. 7 is a flowchart showing an example of an RRC layer of the radioterminal according to the second embodiment;

FIG. 8 is a sequence diagram showing an example of operations of a basestation and a radio terminal according to a third embodiment;

FIG. 9 is a block diagram showing a configuration example of a radioterminal according to some embodiments; and

FIG. 10 is a block diagram showing a configuration example of a basestation according to some embodiments.

DESCRIPTION OF EMBODIMENTS

Hereinafter, specific embodiments will be described in detail withreference to the drawings. The same or corresponding elements aredenoted by the same reference signs throughout the drawings, andrepeated descriptions will be omitted as necessary for the sake ofclarity.

The following descriptions on the embodiments mainly focus on an EvolvedPacket System (EPS) accommodating LTE and SAE (System ArchitectureEvolution). However, these embodiments are not limited to the EPS andmay be applied to other mobile communication networks or systems such as3GPP UMTS, 3GPP2 CDMA 2000 system (1xRTT, High Rate Packet Data (HRPD),global system for mobile communications (GSM (registeredtrademark))/General packet radio service (GPRS), and WiMAX system.

First Embodiment

FIG. 1 illustrates a configuration example of a radio communicationnetwork according to several embodiments including the presentembodiment. In the example illustrated in FIG. 1, the radiocommunication network includes one or more radio terminals (UEs) 1 and abase station (eNB) 2. Each UE 1 includes at least one radio transceiverand is configured to perform cellular communication with the eNB 2. TheeNB 2 manages a cell 21 and is configured to perform cellularcommunication with respective UEs 1 using cellular communicationtechnology (e.g., Evolved Universal Terrestrial Radio Access (E-UTRA)technology).

The eNB 2 illustrated in FIG. 1 may be a Baseband Unit (BBU) used inCentralized Radio Access Network (C-RAN) architecture. In other words,the eNB 2 illustrated in FIG. 1 may be a RAN node connected to one ormore Remote Radio Heads (RRHs). In some implementations, the eNB 2serving as a BBU is in charge of control-plane processing and digitalbaseband signal processing for the user plane. Meanwhile, an RRH is incharge of analog Radio Frequency (RF) signal processing (e.g., frequencyconversion and signal amplification). The C-RAN is also referred to as aCloud RAN. The BBU is also referred to as a Radio Equipment Controller(REC) or a Data Unit (DU). The RRH is also referred to as RadioEquipment (RE), a Radio Unit (RU), or a Remote Radio Unit (RRU).

The eNB 2 transmits access control information (e.g., barringinformation) corresponding to predetermined access barring categories(e.g., ACDC categories). For example, the eNB 2 broadcasts broadcastinformation (i.e., SIB information) 101 containing ACDC controlinformation regarding access control by ACDC. The. ACDC controlinformation broadcasted by the eNB 2 includes barring information perACDC category. Each UE 1 controls whether to allow an access attempt tothe eNB 2 triggered by an application, in accordance with the barringinformation broadcasted by the eNB 2.

FIG. 2 illustrates an example of a protocol stack in the control planeof the UE 1. A control plane protocol stack 200 of the UE 1 includes anapplication (APP) layer 201, a NAS layer 202, and an Access Stratum (AS)208 layer. The AS layer 208 includes an RRC layer 203, a

Packet Data Convergence Protocol (PDCP) layer 204, a Radio Link Control(RLC) layer 205, a Medium Access Control (MAC) layer 206, and a physical(PHY) layer 207.

The NAS layer 202 uses data communication on a radio interface andmanagement of the radio interface provided by the AS layer 208,communicates with a core network (i.e., Evolved Packet Core (EPC)) viathe eNB 2, and provides mobility management (i.e., EPS MobilityManagement (EMM)) and session management (i.e., EPS Session Management(ESM)) for the UE 1. The mobility management (EMM) includes managing oftwo NAS states of the UE 1 related to the connection establishment withthe EPC, i.e., an EMM state (i.e., EMM-DEREGISTERED or EMM-REGISTERED)and an ECM state (i.e., ECM-IDLE or ECM-CONNECTED). The EMM stateindicates whether the UE 1 is registered in a Mobility Management Entity(MME) within the EPC. The ECM state describes the state of the NASsignaling connectivity between the UE 1 and the EPC. ECM-IDLE andECM-CONNECTED may also be referred to as EMM-IDLE and EMM-CONNECTED,respectively.

The mobility management (EMM) protocol implemented in the NAS layer 202includes an attach procedure, a detach procedure, and a Tracking AreaUpdate (TAU) procedure. The mobility management (EMM) protocol furtherincludes procedures for the EMM connection management, i.e., a ServiceRequest procedure and a Transport of NAS messages procedure.

The session management (ESM) includes EPS bearer context managementincluding activation, deactivation, and modification of a user planebearer context (i.e., EPS bearer context). The session management (ESM)further includes requesting by the UE 1 of resources (e.g., IPconnectivity to a Packet Data Network (PDN) or dedicated bearerresources).

The NAS layer 202 communicates with the RRC layer 203 to utilize theservices (i.e., data communication on the radio interface and managementof the radio interface) provided by the AS layer 208. The RRC layer 203,which is a lower layer of the NAS layer 202, provides the radio resourcecontrol (RRC) and manages the RRC state (i.e., RRC_IDLE orRRC_CONNECTED) of the UE 1. The RRC state indicates whether the radioconnection (RRC connection) between the UE 1 and the eNB 2 has beenestablished.

For example, in response to receiving a session establishment requestfrom an upper layer (i.e., the application layer 201), if the UE is inECM-IDLE mode, the NAS layer 202 initiates a Service Request procedureand attempts to send a Service Request message to an MME. The ServiceRequest message from the NAS layer 202 triggers the AS layer 208 toestablish an RRC connection with the eNB 2, and the RRC layer 203initiates an RRC connection establishment procedure. In the presentembodiment, the UE 1 performs ACDC when the UE 1 makes an access attemptto the eNB 2 triggered by a Service Request procedure, Here, the sessionmay be for example, but not limited to, one of S1-MME, S1-U (S1 bearer),network bearer (E-RAB, EPS Bearer, S5/S8 bearer), Radio Bearer, PDNconnection, and IP Connectivity Access Network (IP-CAN) session, or anycombination thereof.

FIG. 3 illustrates an example of the ACDC control information (ACDCInformation Element (IE)) in a case of this control information beingtransmitted in System Information Blok Type 2 (SIB2). As illustrated inFIG. 3, the ACDC control information includes: category information(acdc-Category) with respect to ACDC; and Access Class Barring (ACB)configuration information (acdc-BarringConfig AC-BarringConfig)corresponding to each ACDC category. In addition, the eNB 2 may transmitinformation indicating whether to apply ACDC (or indicating that ACDC isapplied) to each (or a part) of the PLMNS broadcasted in the cell.Furthermore, the eNB 2 may configure these information elements(acdc-Category and acdc-BarringConfig) individually for each (or a part)of the PLMN Identities broadcasted in the cell and transmit theconfigured information elements.

The following describes the operations of the NAS layer 202 and the ASlayer 208 (in particular, the RRC layer 203) for ACDC. In particular,the operations of the NAS layer 202 and the RRC layer 203 of the UE 1performed when the serving network (eNB 2) broadcasts ACDC categoriesfewer than the number of ACDC categories contained in the ACDCconfiguration provisioned in the UE 1 will be described.

FIG. 4 illustrates an example of the ACDC operation in the UE 1. The eNB2 transmits the ACDC control information (ACDC IE) to the UE 1 (401).The ACDC control information includes one or more ACDC categories andbarring information per ACDC category. The eNB 2 may incorporate theACDC control information into broadcast information (e.g., SIBinformation) broadcasted in the cell 21 to enable at least UEs 1 in idlemode (i.e., in ECM-IDLE and RRC_IDLE) to receive the ACDC controlinformation. Here, the eNB 2 may transmit the ACDC control informationconfigured commonly for all the UEs 1 (in idle mode) having the ACDCfunction within the cell or may transmit the ACDC control informationconfigured per PLMN Identity broadcasted within the cell. When the UE 1detects that the ACDC control information is being transmitted per PLMNIdentity, the UE 1 checks whether a PLMN Identity corresponding to thePLMN that the upper layer (i.e., NAS) of the UE 1 has selected issubject to ACDC. When the PLMN Identity is subject to ACDC, the UE 1performs access control of ACDC based on the ACDC control informationconfigured for this PLMN Identity.

The NAS layer 202 of the UE 1 obtains (receives), from the RRC layer203, either or both of: one or more ACDC categories broadcasted by theserving network (eNB 2); and the number of the broadcasted ACDCcategory(ies) (402). In other words, the RRC layer 203 of the UE 1notifies the NAS layer 202 of either or both of: information regardingthe one or more ACDC categories broadcasted by the serving network (eNB2); and the number of the broadcasted ACDC category(ies).

In some implementations, if the number of the one or more ACDCcategories broadcasted by the serving network (eNB 2) is smaller thanthe number of one or more ACDC categories contained in the ACDCconfiguration 410 provisioned in the UE 1, the RRC layer 203 may providethe NAS layer 202 with either or both of: the information regarding theone or more ACDC categories broadcasted by the serving network (eNB 2);and the number of the broadcasted ACDC category(ies).

In this way, the RRC layer 203 is able to provide the NAS layer 202 withthe latest number of ACDC categories in the serving network.

Additionally or alternatively, in response to receiving the updated(i.e., the latest) broadcast information (SIB information) broadcastedby the serving network (eNB 2), if the received broadcast informationcontains the ACDC control information, the RRC layer 203 may provide theNAS layer 202 with either or both of: the information regarding the oneor more ACDC categories broadcasted by the serving network; and thenumber of the broadcasted ACDC category(ies). In this way, the RRC layer203 is able to provide the NAS layer 202 with the latest number of ACDCcategories in the serving network: The RRC layer 203 may provide the NASlayer 202 with the ACDC control information only when the ACDC controlinformation has been updated, or when the broadcast information has beenupdated regardless of whether the ACDC control information has beenupdated.

Additionally or alternatively, if the UE 1 detects that ACDC is beingapplied in the serving network, the RRC layer 203 may provide the NASlayer 202 with either or both of: the information regarding the one ormore ACDC categories broadcasted by the serving network; and the numberof the broadcasted ACDC category(ies).

In response to receiving a request for data transmission (in otherwords, a session establishment request) 403 from the application layer201, if the UE 1 is in idle mode (e.g., ECM-IDLE), the NAS layer 202determines an application identifier of the application that hastriggered the request. The application identifier may include an OS AppID or may be an OS App ID. In some implementations, a combination of anOperating System identifier (OS ID) and an OS App ID is used to identifya particular application. The OS App ID is an OS-specific applicationidentifier.

Furthermore, the NAS layer 202 determines to which ACDC category theapplication that has triggered the request belongs, based on the ACDCconfiguration 410 (404). The ACDC configuration 410 is configured in theUE 1 by a home network operator of the UE 1 and indicates mappingbetween one or more applications installed in the UE 1 (or theirapplication identifiers) and one or more ACDC categories. As describedabove, the ACDC configuration 410 may be configured in the USIMimplemented in the UE 1 by the home network operator. The home networkoperator may configure the ACDC configuration 410 in the UE 1 viaOMA-DM.

When the serving network (i.e., eNB 2) broadcasts fewer ACDC categoriesthan the ACDC configuration 410 provisioned in the UE 1, it is possiblethat the serving network (eNB 2) broadcasts no barring informationcorresponding to the ACDC category (hereinafter referred to as a firstACDC category) to which the application triggering the sessionestablishment request belongs. In other words, it is possible that thefirst ACDC category to which the application triggering the sessionestablishment request belongs is an unmatched ACDC category. The term“unmatched ACDC category” as used herein refers to an ACDC categoryconfigured in the UE 1 but with no corresponding barring informationbroadcasted by the serving network (i.e., eNB 2).

In the present embodiment, if no barring information corresponding tothe first ACDC category (i.e., the value of the first ACDC category) isbroadcasted by the serving network (i.e., eNB 2), the NAS layer 202selects, from the one or more ACDC categories broadcasted by the servingnetwork, a particular ACDC category instead of the first ACDC category(405). In other words, the NAS layer 202 replaces the first ACDCcategory (i.e., the value of the first ACDC category) with a(substitute) particular ACDC category (i.e., the value of the particularACDC category) (405). In other words, the NAS layer 202 considers thatthe application triggering the session establishment request belongs tothe particular ACDC category broadcasted by serving network instead ofto the first ACDC category (405).

In other words, if the serving network (i.e., eNB 2) broadcasts fewerACDC categories than the ACDC configuration 410 provisioned in the UE 1,the NAS layer 202 performs replacement of the ACDC categories in orderto associate each ACDC category contained in the ACDC configuration 410of the UE 1 with any one of the one or more ACDC categories broadcastedby the serving network (i.e., eNB 2) (405).

In one example, when the value of the first ACDC category is greaterthan the maximum value of the one or more ACDC categories (i.e., thevalue of the lowest ACDC category) broadcasted by the serving network,the NAS layer 202 may replace the value of the first ACDC category withthe value of a particular ACDC category. In other words, the NAS layer202 may use the value of a (substitute) particular ACDC category insteadof the value of the first ACDC category.

Alternatively, when the value of the ACDC category corresponding to thevalue of the first ACDC category (and the barring information for thefirst ACDC category) is not broadcasted by the serving network, the NASlayer 202 may replace the value of the first ACDC category with thevalue of a particular ACDC category. In other words, the NAS layer 202may use the value of a (substitute) particular ACDC category instead ofthe value of the first ACDC category.

In some implementations, the particular ACDC category (i.e., substituteACDC category) selected by the NAS layer 202 may be the lowest ACDCcategory among the one or more ACDC categories broadcasted by theserving network (i.e., eNB 2). Such replacement of the ACDC categoriesmay be preferable because the replacement follows the handling of anunmatched ACDC category described in Non-Patent Literature 1.

However, in another implementation, the particular ACDC category (i.e.,substitute ACDC category) selected by the NAS layer 202 need not be thelowest ACDC category in the serving network (i.e., eNB 2). For example,when the number of the ACDC categories broadcasted by the servingnetwork (i.e., eNB 2) is smaller than the number of the ACDC categorieswithin the ACDC configuration 410 provisioned in the UE 1, the NAS layer202 may determine the particular ACDC category (i.e., substitute ACDCcategory), with which the first ACDC category should be replaced, inaccordance with a mapping rule determined in advance. The mapping ruledefines mapping between a plurality of ACDC categories broadcasted (orpossibly broadcasted) by the serving network and one or more ACDCcategories provisioned in the UE 1. The mapping rule may be provisionedin the UE 1 or may be sent to the UE 1 from the serving network (i.e.,eNB 2).

The NAS layer 202 passes the particular ACDC category (i.e., substituteACDC category) selected instead of the first ACDC category to the RRClayer 203 along with a NAS message (i.e., Service Request (SR)) for thesession establishment (406).

Upon receiving the Service Request along with the (substitute) ACDCcategory from the NAS layer 202, the RRC layer 203 performs an ACDCcheck based on the barring information broadcasted from the servingnetwork (i.e., eNB 2) and corresponding to the substitute ACDC category(407). Specifically, the RRC layer 203 controls whether to allow anaccess attempt triggered by the Service Request from the NAS layer 202,based on the barring information broadcasted by the serving network(i.e., eNB 2) and corresponding to the particular ACDC category (i.e.,substitute ACDC category).

FIG. 5 is a flowchart illustrating an example (process 500) of theoperation regarding ACDC performed by the NAS layer 202 of the UE 1. Inblock 501, the NAS layer 202 obtains, from the RRC layer 203, the numberof ACDC categories broadcasted by the serving network (i.e., eNB 2). Inblock 502, the NAS layer 202 determines the first ACDC category to whichthe application triggering the session establishment request belongs,based on the ACDC configuration 410 provisioned in the UE 1 by the homenetwork operator.

In block 503, when no barring information corresponding to the firstACDC category is broadcasted by the serving network (i.e., eNB 2), theNAS layer 202 replaces the first ACDC category with a particular ACDCcategory among the one or more ACDC categories broadcasted by theserving network. In block 504, the NAS layer 202 passes the (substitute)particular ACDC category along with the Service Request to the RRC layer203.

In order for the NAS layer 202 to pass the ACDC category along with theService Request to the RRC layer 203, a new call type may be defined.The NAS layer 202 informs the RRC layer 203 of the call type whenrequesting the RRC layer 203 to establish a NAS signaling connection totransmit an initial NAS message (e.g., Service Request). Existing calltype indicates “originating calls”, “terminating calls”, “emergencycalls”, or “originating signaling”. In addition to the above, when anapplication triggering session establishment belongs to an ACDC categoryX, the new call type may be, for example, “ACDC Cat-X originatingcalls”. By receiving the new call type, the RRC layer 203 is able toknow the ACDC category to which the application triggering the accessattempt (i.e., attempt for RRC connection establishment) belongs.

Alternatively, a new information element different from the call typemay be defined to represent an ACDC category. The new informationelement may be, for example, “ACDC Category Indication”, “EstablishedACDC Category”, “Triggered ACDC category”, “Selected ACDC Category”, or“Assigned ACDC Category”. In this case, the NAS layer 202 may pass, tothe RRC layer 203, the new information element along with the initialNAS message (e.g., Service Request) and the call type (e.g., originatingcalls). By receiving the new information element, the RRC layer 203 isable to know the ACDC category to which the application triggering theaccess attempt (i.e., attempt for RRC connection establishment) belongs.

As can be understood from the foregoing description, in the exampledescribed with reference to FIG. 4 and FIG. 5, when barring informationcorresponding to the first ACDC category to which the applicationtriggering the session establishment request belongs is not broadcastedby the serving network (i.e., eNB 2), the NAS layer 202 replaces thefirst ACDC category with a substitute ACDC category and sends (orpasses) the substitute ACDC category to the RRC layer 203, Thesubstitute ACDC category is one of the one or more ACDC categoriesbroadcasted by the serving network. In other words, if the servingnetwork (eNB 2) broadcasts fewer ACDC categories than the ACDCconfiguration 410 provisioned in the UE 1, the NAS layer 202 performsreplacement of the ACDC categories in order to associate each ACDCcategory contained in the ACDC configuration 410 of the UE 1 with anyone of the one or more ACDC categories broadcasted by the servingnetwork (i.e., eNB 2). The RRC layer 203 then performs an ACDC checkbased on the barring information broadcasted by the serving network(i.e., eNB and corresponding to the substitute ACDC category.

That is, according to the example described with reference to FIG. 4 andFIG. 5, the NAS layer 202 of the UE 1 is able to perform the replacementof the ACDC categories, and the RRC layer 203 of the UE 1 is able toperform the ACDC check.

In one example, the NAS layer 202 may release the information regardingthe (substitute) particular ACDC category each time the UE 1 changes itsserving cell. Alternatively, the NAS layer 202 may retain theinformation regarding the particular ACDC category even when the UE 1has changed its serving cell. For example, the NAS layer 202 may retainthe information regarding the particular ACDC category while the UE 1has selected the same PLMN (or the same serving network) and while theACDC function is activated in the serving cell(s) after changing itsserving cell.

Second Embodiment

This embodiment provides a modification example of the ACDC operation inthe UE 1 described in the first embodiment. Specifically, an example inwhich the RRC layer 203, instead of the NAS layer 202, performs thereplacement of the ACDC categories will be described. The configurationexample of the radio communication network according to the presentembodiment is similar to that illustrated in FIG. 1, and the controlplane protocol stack of the UE 1 is similar to that illustrated in FIG.2.

FIG. 6 illustrates an example of the ACDC operation in the UE 1. The eNB2 transmits ACDC control information to the UE 1 (601). The ACDC controlinformation includes a plurality of ACDC categories and barringinformation per ACDC category. The eNB 2 may incorporate the ACDCcontrol information into broadcast information (e.g., SIB information)broadcasted in the cell 21 to enable the UE 1 in idle mode (i.e., inECM-IDLE and RRC_IDLE) to receive the ACDC control information.

In response to receiving a request for data transmission (in otherwords, a session establishment request) 602 from the application layer201, if the UE 1 is in idle mode (ECM-IDLE), the NAS layer 202determines an application identifier of the application that hastriggered the request. The application identifier may include an. OS AppID or may be an OS App ID. Furthermore, the NAS layer 202 determines towhich ACDC category the application that has triggered the requestbelongs based on the ACDC configuration 610 (603). The ACDCconfiguration 610 is similar to the ACDC configuration 410 illustratedin FIG. 4. In other words, the ACDC configuration 610 indicates mappingbetween a plurality of applications (application identifiers) installedin the UE 1 (or their application identifiers) and a plurality of ACDCcategories. The ACDC configuration 610 is provisioned in the UE 1, forexample, via OMA-DM or USIM.

The NAS layer 202 passes, to the RRC layer 203, the ACDC category towhich the application that triggers the session establishment requestbelongs (i.e., the ACDC category derived from the ACDC configuration610) along with a NAS message for session establishment (i.e., ServiceRequest (SR)) (604).

As described with reference to FIG. 4, when the serving network (i.e.,eNB 2) broadcasts fewer ACDC categories than the ACDC configuration 410provisioned in the UE 1, it is possible that the serving network (i.e.,eNB 2) broadcasts no barring information corresponding to the ACDCcategory (hereinafter referred to as a first ACDC category) to which theapplication that triggers the session establishment request belongs. Inother words, it is possible that the ACDC category to which theapplication that triggers the session establishment request belongs isan unmatched ACDC category. The term “unmatched ACDC category” as usedherein refers to an ACDC category configured in the UE 1 but with nocorresponding barring information broadcasted by the serving network(i.e., eNB 2).

In the present embodiment, if no barring information corresponding tothe first ACDC category is broadcasted by the serving network (i.e., eNB2), the RRC layer 203 selects, from the one or more ACDC categoriesbroadcasted by the serving network, a particular ACDC category insteadof the first ACDC category (605). In other words, the

RRC layer 203 replaces the first ACDC category with a (substitute)particular ACDC category (605). In other words, the RRC layer 203considers that the application that triggers the session establishmentrequest belongs to a particular ACDC category broadcasted by servingnetwork (605), instead of to the first ACDC category.

In other words, if the serving network (i.e., eNB 2) broadcasts fewerACDC categories than the ACDC configuration 610 provisioned in the UE 1,the RRC layer 203 performs replacement of the ACDC categories in orderto associate each ACDC category contained in the ACDC configuration 610of the UE 1 with any one of the one or more ACDC categories broadcastedby the serving network (i.e., eNB 2) (605).

In one example, when the value of the first ACDC category is greaterthan the maximum value of the one or more ACDC categories (i.e., thevalue of the lowest ACDC category) broadcasted by the serving network,the RRC layer 203 may replace the value of the first ACDC category withthe value of the (substitute) particular ACDC category. In other words,the RRC layer 203 may use the value of the (substitute) particular ACDCcategory instead of the value of the first ACDC category.

Alternatively, when the value of the ACDC category corresponding to thevalue of the first ACDC category (and the barring information for thefirst ACDC category) is not broadcasted by the serving network, the RRClayer 203 may replace the value of the first ACDC category with thevalue of the particular ACDC category. In other words, the RRC layer 203may use the value of the (substitute) particular ACDC category insteadof the value of the first ACDC category.

In some implementations, the particular ACDC category (i.e., substituteACDC category) selected by the RRC layer 203 may be the lowest ACDCcategory among the one or more ACDC categories broadcasted by theserving network (i.e., eNB 2). Such replacement of ACDC categories maybe preferable because the replacement follows the handling of anunmatched ACDC category described in Non-Patent Literature 1.

However, in another implementation, the particular ACDC category (i.e.,substitute ACDC category) selected by the RRC layer 203 need not be thelowest ACDC category in the serving network (i.e., eNB 2). For example,when the number of ACDC categories broadcasted by the serving network(i.e., eNB 2) is smaller than the number of ACDC categories within theACDC configuration 610 provisioned in the UE 1, the RRC layer 203 maydetermine the particular ACDC category (i.e., substitute ACDC category),with which the first ACDC category should be replaced, in accordancewith a mapping rule determined in advance. The mapping rule definesmapping between a plurality of ACDC categories broadcasted (or possiblybroadcasted) by the serving network and one or more ACDC categoriesprovisioned in the UE 1. The mapping rule may be provisioned in the UE 1or may be sent to the UE 1 from the serving network (i.e., eNB 2).

The RRC layer 203 performs an ACDC check based on the barringinformation broadcasted by the serving network (i.e., eNB 2) andcorresponding to the substitute ACDC category (606). In other words, theRRC layer 203 controls whether to allow an access attempt triggered bythe Service Request from the NAS layer 202, based on the barringinformation broadcasted by the serving network (i.e., eNB 2) andcorresponding to the particular ACDC category (substitute ACDCcategory).

FIG. 7 is a flowchart illustrating an example (process 700) of theoperation regarding ACDC performed by the RRC layer 203 of the UE 1. Inblock 701, the RRC layer 203 receives one or more ACDC categories andbarring information broadcasted by the serving network (eNB 2).

In block 702, the RRC layer 203 receives the first ACDC category, towhich the application that triggers the session establishment requestbelongs, from the NAS layer 202 along with a Service Request. Asdescribed above, the first ACDC category is derived by the NAS layer 202from the ACDC configuration 610 provisioned in the UE 1.

In block 703, when no barring information corresponding to the firstACDC category is broadcasted by the serving network (i.e., eNB 2), theRRC layer 203 selects, from the one or more ACDC categories broadcastedby the serving network, a particular ACDC category instead of the firstACDC category.

In block 704, the RRC layer 203 controls whether to allow the accessattempt based on the barring information broadcasted by the servingnetwork (i.e., eNB 2) and corresponding to the particular ACDC category.

As described in the first embodiment, in order for the NAS layer 202 topass the ACDC category along with the Service Request to the RRC layer203, a new call type may be defined. The NAS layer 202 informs the RRClayer 203 of the call type when requesting the RRC layer 203 toestablish a NAS signaling Connection to transmit an initial NAS message(e.g., Service Request). Existing call type indicates “originatingcalls”, “terminating calls”, “emergency calls”, or “originatingsignaling”. In addition to the above, when the application that triggersthe session establishment belongs to an ACDC category X, the new calltype may be, for example, “ACDC Cat-X originating calls”.

By receiving the new call type, the RRC layer 203 is able to know thefirst ACDC category to which the application that triggers the accessattempt (i.e., attempt for RRC connection establishment) belongs. Ifbarring information corresponding to the first ACDC category specifiedby the new call type is not broadcasted by the serving network or if theRRC layer 203 cannot recognize the new call type (or if the new calltype is an “unknown call type”), the RRC layer 203 may select asubstitute ACDC category.

Alternatively, a new information element different from the call typemay be defined to represent an ACDC category. The new informationelement may be, for example, “ACDC Category Indication”, “EstablishedACDC Category”, “Triggered ACDC category”, “Selected ACDC Category”, or“Assigned ACDC Category”. In this case, the NAS layer 202 may pass, tothe RRC layer 203, the new information element along with the initialNAS message (e.g., Service Request) and with the call type (e.g.,originating calls). By receiving the new information element, the RRClayer 203 is able to know the first ACDC category to which theapplication that triggers the access attempt (i.e., attempt for RRCconnection establishment) belongs. When no barring informationcorresponding to the first ACDC category specified by the newinformation element is broadcasted by the serving network or when theRRC layer 203 cannot recognize the first ACDC category specified by thenew information element (or when the first ACDC category is an “unknownACDC category”), the RRC layer 203 may select a substitute ACDCcategory.

As can be understood from the foregoing description, in the exampledescribed with reference to FIG. 6 and FIG. 7, when barring informationcorresponding to the first ACDC category to which the application thattriggers the session establishment request belongs is not broadcasted bythe serving network (i.e., eNB 2), the RRC layer 203 selects asubstitute ACDC category instead of the first ACDC category and performsan ACDC check based on the barring information broadcasted by theserving network (i.e., eNB 2) and corresponding to the substitute ACDCcategory. In other words, if the serving network (i.e., eNB 2)broadcasts fewer ACDC categories than the ACDC configuration 610provisioned in the UE 1, the RRC layer 203 performs replacement of theACDC categories in order to associate each ACDC category contained inthe ACDC configuration 610 of the UE 1 with any one of the one or moreACDC categories broadcasted by the serving network (i.e., eNB 2).

That is, according to the example described with reference to FIG. 6 andFIG. 7, the RRC layer 203 of the UE 1 is able to perform the replacementof the ACDC categories and the ACDC check.

Third Embodiment

This embodiment provides a modification example of the ACDC operation inthe UE 1 described in the first and second embodiments. Theconfiguration example of a radio communication network according to thepresent embodiment is similar to that illustrated in FIG. 1, and thecontrol plane protocol stack of the UE 1 is similar to that illustratedin FIG. 2.

As described in the first and second embodiments, when the servingnetwork (i.e., eNB 2) broadcasts fewer ACDC categories than the ACDCconfiguration 410 or 610 provisioned in the UE 1, the NAS layer 202 orthe RRC layer 203 selects a substitute ACDC category. At this point, theNAS layer 202 or the RRC layer 203 may select the substitute ACDCcategory in accordance with a mapping rule sent from the serving network(i.e., eNB 2). The mapping rule defines mapping between a plurality ofACDC categories broadcasted (or possibly broadcasted) by the servingnetwork and one or more ACDC categories provisioned in the UE 1.

FIG. 8 is a sequence diagram illustrating an example (process 800) of aprocedure for sending the mapping rule from the eNB 2 to the UE 1. Instep 801, the eNB 2 transmits, to the UE 1, a plurality of ACDCcategories used in the cell 21, barring information per ACDC category,and the mapping rule between the ACDC categories broadcasted by the eNB2 and the ACDC categories provisioned in the UE 1. The eNB 2 maytransmits broadcast information (SIB information) containing the aboveinformation in the cell 21.

For example, a case in which the ACDC configuration (410 or 610) withinthe UE 1 defines five ACDC categories and the serving network (i.e., eNB2) defines three ACDC categories will be considered. In this case, themapping rule may associate the highest ACDC category within the ACDCconfiguration of the UE 1 to the highest ACDC category of the servingnetwork, associate the second and third highest ACDC categories withinthe ACDC configuration of the UE 1 to the second highest ACDC categoryof the serving network, and associate the fourth and fifth highest ACDCcategories within the ACDC configuration of the UE 1 to the thirdhighest (i.e., the lowest) ACDC category of the serving network.

The eNB 2 may provide a plurality of mapping rules to the UE 1 in orderto associate a specific ACDC category number (e.g., 3) used in theserving network (eNB 2) with a plurality of ACDC category numbers (e.g.,4, 5, 6, . . . ) provisioned in the UE 1.

In the present embodiment, the serving network (i.e., eNB 2) is able toexplicitly indicate, to the UE 1, the mapping between the ACDC categorynumbers used in the serving network (eNB 2) and the ACDC categorynumbers provisioned in the UE 1

In one example, the AS layer 208 (RRC layer 203) may release theinformation regarding the (substitute) particular ACDC category eachtime the UE 1 changes its serving cell. Alternatively, the AS layer 208(RRC layer 203) may retain the information regarding the particular ACDCcategory even when the UE 1 has changed its serving cell. For example,the AS layer 208 (RRC layer 203) may retain the information regardingthe particular ACDC category while the UE 1 has selected the same PLMN(or the same serving network) and while the ACDC function is activatedin the changed serving cell(s).

Fourth Embodiment

This embodiments described above assume a case in which the UE 1 in idlemode (e.g., RRC_IDLE) is subject to ACDC. In the present embodiment,ACDC is applied to the UE 1 in connected mode (e.g., RRC_CONNECTED). Inother words, in this embodiment, it is assumed that ACDC is used in theUE 1 when the UE 1 already in connected mode is to start a newapplication (or service). In this case, it is conceivable that ACDCimplements control for a service request restriction on a servicerequest) on an RRC_CONNECTED terminal, instead of access control (i.e.,access restriction) on an RRC_IDLE terminal. Here, the control(restriction) on the Service Request in the UE 1 in RRC_CONNECTED may bea control (prevention) of transmission of a Scheduling Request torequest an uplink resource to be assigned by the eNB 2 in order totransmit a Service Request from the UE 1 to start the application (orservice). Alternatively, when the UE 1 in RRC_CONNECTED is notconfigured with control resources (Physical Uplink Control Channel(PUCCH)) for transmitting the Scheduling Request (i.e., uplink recourserequest) or when the uplink synchronization state of the UE 1 is“non-synchronised” or “out-of-sync,” the control (restriction) on theService Request in the UE 1 in RRC_CONNECTED may be a control(prevention) of initiation of a random access procedure (i.e.,transmission of a random access preamble).

The UE 1 may perform, for example, a procedure as follows. The UE 1establishes a radio connection (RRC Connection) with the eNB 2 in thecell 21 of the eNB 2 and enters the RRC_CONNECTED state. In one case,the UE 1 may enter the RRC_CONNECTED state after performing

ACDC (i.e., after performing the access control of ACDC). Alternatively,in another case, ACDC may not be activated (i.e., the eNB 2 has notbroadcasted the ACDC control information) in the serving cell (withrespect to the serving network of the PLMN selected by the NAS layer ofthe UE 1) at the point when the UE 1 enters the RRC_CONNECTED state, andthus the UE 1 may have entered the RRC_CONNECTED state withoutperforming ACDC.

Thereafter, when a trigger that starts a new application (or service) inthe UE 1 in the RRC_CONNECTED state occurs, the UE 1 checks whether.ACDC has been activated in the serving cell (i.e., whether the eNB 2 hasbroadcasted the ACDC control information). When the ACDC has beenactivated, the NAS layer or the RRC layer of the UE 1 performs thematching between the ACDC configuration provisioned in the UE 1 and theACDC control information broadcasted in the serving cell. Specifically,the NAS layer or the RRC layer of the UE 1 checks whether the barringinformation corresponding to the first ACDC category that corresponds tothe application (or service) is broadcasted. When no barring informationcorresponding to the first ACDC category is broadcasted, the UE 1selects a particular ACDC category as a substitute for the first ACDCcategory. The matching between the ACDC configuration and the ACDCcontrol information can be implemented using a procedure similar to thatdescribed in the first embodiment or the second embodiment, and thusdetailed description thereof will be omitted.

After that, the RRC layer of the UE 1 performs a Service Request (e.g.,instruction to the MAC layer to transmit a Scheduling Request or tostart a random access procedure) based on the barring informationcorresponding to the first ACDC category or to the replaced particularACDC category. For example, when the barring information does not allowthe application (service) to send the Service Request, the UE 1 does notperform the Service Request in the serving cell for a predeterminedperiod or until ACDC is deactivated. Alternatively, when the ServiceRequest is allowed at a predetermined probability, the UE 1 may performthe Service Request in accordance with this probability.

In this way, the access control (in this case, the Service Requestrestriction) can be performed even on the UE 1 already in theRRC_CONNECTED state, and the overload of the network can be prevented ormitigated. ACDC on the RRC_CONNECTED terminal may be performed on aper-terminal basis or on a per group-of-terminals basis. In addition,the eNB 2 may transmit at least a portion of the ACDC controlinformation to the UE 1 using a terminal dedicated message (e.g., RRCConnection Reconfiguration message). In this case, the UE 1 maypreferentially use the configuration specified by the terminal dedicatedmessage over the configuration specified by the broadcasted ACDC controlinformation.

Lastly, a configuration example of the UE 1 according to theabove-described embodiments will be described. FIG. 9 is a block diagramshowing a configuration example of the UE 1 according to the aboveembodiments. A. Radio Frequency (RF) transceiver 901 performs analog RFsignal processing to communicate with the eNB 2. The analog RF signalprocessing performed by the RF transceiver 901 includes frequencyup-conversion, frequency down-conversion, and amplification. The RFtransceiver 901 is coupled to an antenna 902 and a baseband processor903. That is, the RF transceiver 901 receives modulation symbol data (orOFDM symbol data) from the baseband processor 903, generates atransmission RF signal, and supplies the transmission RF signal to theantenna 902. Moreover, the RF transceiver 901 generates a basebandreception signal based on a reception RF signal received by the antenna902, and supplies the baseband reception signal to the basebandprocessor 903.

The baseband processor 903 performs digital baseband signal processing(i.e., data plane processing) and control plane processing for radiocommunication. The digital baseband signal processing includes (a) datacompression/decompression, (b) data segmentation/concatenation, (c)generation/decomposition of a transmission format (transmission frame),(d) transmission channel coding/decoding, (e) modulation (symbolmapping)/demodulation, (f) generation of OFDM symbol data (baseband OFDMsignal) by Inverse Fast Fourier Transform (IFFT), and the like. On theother hand, the control plane processing includes communicationmanagement in the layer 1 (e.g., transmission power control), layer 2(e.g., radio resource management and hybrid automatic repeat request(HARQ) processing), and layer 3 (e.g., signaling regarding attach,mobility, and call management).

For example, in the case of LTE and LTE-Advanced, the digital basebandsignal processing performed by the baseband processor 903 may includesignal processing in the Packet Data Convergence Protocol (PDCP) layer,Radio Link Control (RLC) layer, MAC layer, and PHY layer. Further, thecontrol plane processing by the baseband processor 903 may include theprocessing of the Non-Access Stratum (NAS) protocol, RRC protocol, andMAC CE.

The baseband processor 903 may include a modern processor (e.g., DigitalSignal Processor (DSP)) that performs the digital baseband signalprocessing and a protocol stack processor (e.g., Central Processing Unit(CPU) or Micro Processing Unit (MPU)) that performs the control planeprocessing. In this case, the protocol stack processor that performs thecontrol plane processing may be integrated with an application processor904 described in the following.

The application processor 904 is also referred to as a CPU, an MPU, amicroprocessor, or a processor core. The application processor 904 mayinclude a plurality of processors (a plurality of processor cores). Theapplication processor 904 loads a system software program (OperatingSystem (OS)) and various application programs (e.g., a call application,a WEB browser, a mailer, a camera operation application, a musicplayback application) from a memory 906 or from another memory (notshown) and executes these programs, thereby providing various functionsof the UE 1.

In some implementations, as indicated by the dashed line (905) in FIG.9, the baseband processor 903 and the application processor 904 may beintegrated on a single chip. In other words, the baseband processor 903and the application processor 904 may be implemented in one System onChip (SoC) device 905. A SoC device is sometimes referred to as a systemLarge Scale Integration (LSI) or a chipset.

The memory 906 is a volatile memory or a non-volatile memory or acombination thereof. The memory 906 may include a plurality ofphysically independent memory devices. The volatile memory is, forexample, Static Random Access Memory (SRAM), Dynamic RAM (DRAM) or acombination thereof. The non-volatile memory may he a Mask Read OnlyMemory (MROM), an Electrically Erasable Programmable ROM (EEPROM), aflash memory, a hard disk drive, or any combination thereof. The memory906 may include an external memory device accessible from the basebandprocessor 903, the application processor 904, and the SoC 905. Thememory 906 may include an internal memory device integrated within thebaseband processor 903, the application processor 904, or the SoC 905.The memory 906 may further include a memory in a Universal IntegratedCircuit Card (UICC).

The memory 906 may store a software module(s) (computer program(s))including instructions and data for processing by the UE 1 described inthe above embodiments. In some implementations, the baseband processor903 or the application processor 904 may be configured to load thesoftware module(s) from the memory 906 and execute the loaded softwaremodule(s), thereby performing the processing of the remote UE 1described in the above embodiments.

FIG. 10 is a block diagram showing a configuration example of the basestation (eNB) 2. Referring to FIG. 10, the base station 2 includes an RFtransceiver 1001, a network interface 1003, a processor 1004, and amemory 1005. The RF transceiver 1001 performs analog RF signalprocessing to communicate with the radio terminal 1. The RF transceiver1001 may include a plurality of transceivers. The RF transceiver 1001 iscoupled to an antenna 1002 and a processor 1004. The RF transceiver 1001receives modulation symbol data (or OFDM symbol data) from the processor1004, generates a transmission RF signal, and supplies the transmissionRF signal to the antenna 1002. Moreover, the RF transceiver 1001generates a baseband reception signal based on a reception RF signalreceived by the antenna 1002, and supplies the baseband reception signalto the processor 1004.

The network interface 1003 is used to communicate with network nodes(e.g., Mobility Management Entity (MME) and Serving Gateway (S-GW)). Thenetwork interface 1003 may include, for example, a network interfacecard (NIC) conforming to the IEEE 802.3 series.

The processor 1004 performs digital baseband signal processing (i.e.,data plane processing) and control plane processing for radiocommunication. For example, in the case of LTE and LTE-Advanced, thedigital baseband signal processing performed by the processor 1004 mayinclude signal processing of the PDCP layer, RLC layer, MAC layer, andPHY layer. Further, the control plane processing performed by theprocessor 104 may include processing of the S1 protocol, RRC protocol,and MAC CE.

The processor 1004 may include a plurality of processors. The processor1004 may include, for example, a modem processor (e.g., DSP) thatperforms the digital baseband signal processing and a protocol stackprocessor (e.g., CPU or MPU) that performs the control plane processing.

The memory 1205 is composed of a combination of a volatile memory and anon-volatile memory. The memory 1205 may include a plurality ofphysically independent memory devices. The volatile memory is, forexample, SRAM, DRAM or a combination thereof. The non-volatile memorymay be a MROM, an EEPROM, a flash memory, a hard disk drive, or anycombination thereof. The memory 1005 may include a storage disposedseparately from the processor 1004. In this case, the processor 1004 mayaccess the memory 1005 via the network interface 1003 or a notillustrated I/O interface.

The memory 1005 may store a software module(s) (computer program(s))including instructions and data for processing by the base station 2described in the above embodiments. In some implementations, theprocessor 1004 may be configured to load the software module(s) from thememory 1005 and execute the loaded software module(s), therebyperforming the processing of the base station 2 described in the aboveembodiments.

As described with reference to FIGS. 9 and 10, each of the processorsincluded in the UE 1 and eNB 2 according to the above-describedembodiments executes one or more programs including instructions forcausing a computer to perform the algorithm described with reference tothe drawings. These programs can be stored and provided to a computerusing any type of non-transitory computer readable media. Non-transitorycomputer readable media include any type of tangible storage media.Examples of non-transitory computer readable media include magneticstorage media (such as floppy disks, magnetic tapes, hard disk drives,etc.), optical magnetic storage media (e.g. magneto-optical disks),Compact Disc Read Only Memory (CD-ROM), CD-R, CD-R/W, semiconductormemories (such as Mask ROM, Programmable ROM (PROM), Erasable PROM(EPROM), flash ROM, Random Access Memory(RAM)). These programs can bestored and provided to a computer using any type of transitory computerreadable media. Examples of transitory computer readable media includeelectric signals, optical signals, and electromagnetic waves. Transitorycomputer readable media can provide programs to a computer via a wiredcommunication line (e.g. electric wires, and optical fibers) or awireless communication line.

Other Embodiments

Each of the above embodiments may be used individually, or two or moreof the embodiments may be appropriately combined with one another.

The UE 1 (NAS layer 202 or AS layer 208) capable of retaining theinformation regarding the particular ACDC category even the serving cellhas been changed as described as an example in the foregoing embodimentsmay, when the serving network (eNB 2) is changed to another network(second network) having a different PLMN Identity, discard, release, ormodify the particular ACDC category selected instead of, replaced with,or regarded as belonging to the first ACDC category for the servingnetwork (first network) that has not been changed.

Here, the case in which the UE 1 has changed the serving network to thesecond network may be a case in which the UE 1 has made a handover(Iinter-PLMN HO) from the first network to the second network or may bea case in which the UE 1 has changed the serving network from the firstnetwork to the second network by making a network selection (PLMNselection) in idle mode (e.g., RRC IDLE).

Alternatively, in response to receiving the information regarding theone or more ACDC categories broadcasted from the second network, the UE1 may discard, release, or modify the particular ACDC category selectedinstead of, replaced with, or regarded as belonging to the first ACDCcategory for the first network.

For example, in the case of the first embodiment, in response toobtaining (receiving), from the RRC layer 203, either or both of theinformation regarding the one or more ACDC categories broadcasted by thesecond network and the number of broadcasted ACDC category(ies) (203),the NAS layer 202 may discard, release, or modify the previousconfiguration (i.e., substitute particular ACDC category) within the NASlayer 202, but this is not a limiting example.

In the case of the second embodiment, in response to receiving the ACDCcontrol information broadcasted by the second network (501), the RRClayer 203 may discard, release, or modify the previous configuration(i.e., substitute particular ACDC category) within the RRC layer 203,but this is not a limiting example.

According to the above, ACDC can be performed appropriately even whenthe UE 1 capable of retaining the information regarding the particularACDC category even when the serving cell has been changed changes theserving network from the first network of one PLMN to the second networkof another PLMN. For example, a case in which the

ACDC category provisioned in advance in the UE 1 is 4, the ACDCcategories provided by the first network are 1 to 3, and the ACDCcategories provided by the second network are 1 to 4 will be considered.When the UE 1 moves to the second network after replacing the first ACDCcategory=4 with the particular ACDC category=3 for the first network,the UE 1 can discard (release) the configuration of the substituteparticular ACDC category for the first network, and thus the UE 1 canappropriately perform ACDC in the second network.

In the embodiments described above, the eNB 2 may share informationregarding ACDC performed in its own cell(s) (e.g., ACDC controlinformation, or information about whether ACDC is being performed ornot) with neighbour eNBs. In addition, the eNB 2 may transmit, in one ofits cells, information regarding ACDC performed in adjacent cells (e.g.,other cells of the eNB .2, or cells of other eNBs). The UE 1 may performcell reselection based on the information regarding ACDC performed inthe adjacent cell(s).

The embodiments described above are not limited to LTE, LTE-Advanced,and improvements thereof and may also be applied to application-specificaccess barring (or congestion control) in other radio communicationnetworks and systems.

Further, the above-described embodiments are merely examples ofapplications of the technical ideas obtained by the inventor. Thetechnical ideas are not limited to the above-described embodiments, andvarious changes and modifications may be made thereto.

The present application is based upon and claims the benefit of priorityfrom Japanese Patent Application No. 2015-148790, filed on Jul. 28,2015, the entire contents of which are hereby incorporated by reference.

REFERENCE SIGNS LIST

-   1 RADIO TERMINAL (UE)-   2 BASE STATION (eNB)-   901 RADIO FREQUENCY (RF) TRANSCEIVER-   903 BASEBAND PROCESSOR-   904 APPLICATION PROCESSOR-   906 MEMORY p0 1001 RF TRANSCEIVER-   1004 PROCESSOR-   1005 MEMORY

1. A radio terminal, comprising: a radio transceiver; and at least oneprocessor coupled to the radio transceiver and configured to operate asa non-access stratum (NAS) layer providing mobility management andsession management and as an access stratum (AS) layer providing radioresource control, wherein the NAS layer is adapted to obtain, from theAS layer, either or both of: information regarding one or more accessbarring categories broadcasted by a serving network; and the number ofthe one or more access barring categories, the NAS layer is adapted to,if barring information corresponding to a first access barring categoryto which an application that triggers a session establishment belongs isnot broadcasted by the serving network, replace the first access barringcategory with a particular access barring category among the one or moreaccess barring categories broadcasted by the serving network, the NASlayer is adapted to pass the particular access barring category alongwith a NAS message for the session establishment to the AS layer, andthe AS layer is adapted to control whether to allow an access attempttriggered by the NAS layer based on barring information broadcasted bythe serving network and corresponding to the particular access barringcategory.
 2. The radio terminal according to claim 1, wherein the ASlayer is adapted to, when the number of the one or more access barringcategories broadcasted by the serving network is smaller than the numberof access barring categories contained in configuration informationprovisioned in the radio terminal, provide the NAS layer with either orboth of: the information regarding the one or more access barringcategories broadcasted by the serving network; and the number of the oneor more access barring categories.
 3. The radio terminal according toclaim 1, wherein the AS layer is adapted to, in response to receivinglatest broadcast information broadcasted by the serving network, providethe NAS layer with either or both of: the information regarding the oneor more access barring categories broadcasted by the serving network;and the number of the one or more access barring categories.
 4. Theradio terminal according to claim 1, wherein the AS layer is adapted to,when the wireless terminal detects that access barring is being appliedin the serving network, provide the NAS layer with either or both of:the information regarding the one or more access barring categoriesbroadcasted by the serving network; and the number of the one or moreaccess barring categories.
 5. The radio terminal according to claim 1,wherein the NAS layer is adapted to, upon receiving a request for thesession establishment from the application, if the radio terminal is inidle mode, determine to which access barring category the applicationbelongs based on configuration information provisioned in the radioterminal.
 6. The radio terminal according to claim 1, wherein theparticular access barring category corresponds to a lowest accessbarring category among the one or more access barring categoriesbroadcasted by the serving network.
 7. The radio terminal according toclaim 1, wherein the NAS layer is adapted to obtain, from the AS layer,a mapping rule broadcasted by the serving network, the mapping ruledefines mapping between the one or more access barring categoriesbroadcasted by the serving network and one or more access barringcategories provisioned in the radio terminal, and the NAS layer isadapted to determine the particular access barring category with whichthe first access barring category is to be replaced in accordance withthe mapping rule. 8-13. (canceled)
 14. A radio terminal, comprising: aradio transceiver; and at least one processor coupled to the radiotransceiver and configured to operate as a non-access stratum (NAS)layer providing mobility management and session management and as anaccess stratum (AS) layer providing radio resource control, wherein theNAS layer is adapted to pass a first access barring category to which anapplication that triggers a session establishment belongs, along with aNAS message for the session establishment to the AS layer, the AS layeris adapted to, if barring information corresponding to the first accessbarring category received from the NAS layer is not broadcasted by aserving network, select, from one or more access barring categoriesbroadcasted by the serving network, a particular access barring categoryinstead of the first access barring category, and the AS layer isadapted to control whether to allow an access attempt triggered by theNAS layer based on barring information broadcasted by the servingnetwork and corresponding to the particular access barring category. 15.The radio terminal according to claim 14, wherein the NAS layer isadapted to send, to the AS layer, a call type indicating the firstaccess barring category in order to pass the first access barringcategory to the AS layer, and the AS layer is adapted to select theparticular access barring category instead of the first access barringcategory, when barring information corresponding to the first accessbarring category specified by the call type is not broadcasted by theserving network, or when the AS layer cannot recognize the call type.16. The radio terminal according to claim 14, wherein the NAS layer isadapted to, upon receiving a request for the session establishment fromthe application, if the radio terminal is in idle mode, determine towhich access barring category the application belongs based onconfiguration information provisioned in the radio terminal.
 17. Theradio terminal according to claim 14, wherein the particular accessbarring category corresponds to a lowest access barring category amongthe one or more access barring categories broadcasted by the servingnetwork.
 18. The radio terminal according to claim 14, wherein the ASlayer is adapted to determine the particular access barring category tobe selected instead of the first access barring category in accordancewith a mapping rule broadcasted by the serving network, and the mappingrule defines mapping between the one or more access barring categoriesbroadcasted by the serving network and one or more access barringcategories provisioned in the radio terminal.
 19. A method in a radioterminal, the method comprising: passing, from a non-access stratum(NAS) layer to an access stratum (AS) layer, a first access barringcategory to which an application that triggers a session establishmentbelongs, along with a NAS message for the session establishment; ifbarring information corresponding to the first access barring categoryreceived from the NAS layer is not broadcasted by a serving network,selecting by the AS layer, from one or more access barring categoriesbroadcasted by the serving network, a particular access barring categoryinstead of the first access barring category; and controlling, by the ASlayer, whether to allow an access attempt triggered by the NAS layerbased on barring information broadcasted by the serving network andcorresponding to the particular access barring category.
 20. The methodaccording to claim 20, wherein the passing includes sending, to the ASlayer, a call type indicating the first access barring category, and theselecting includes selecting, by the AS layer, the particular accessbarring category instead of the first access barring category, whenbarring information corresponding to the first access barring categoryspecified by the call type is not broadcasted by the serving network, orwhen the AS layer cannot recognize the call type.
 21. The methodaccording to claim 19, wherein the selecting includes determining, bythe AS layer, the particular access barring category to be selectedinstead of the first access barring category in accordance with amapping rule broadcasted by the serving network, and the mapping ruledefines mapping between the one or more access barring categoriesbroadcasted by the serving network and one or more access barringcategories provisioned in the radio terminal. 22-27. (canceled)